The federal government of the United States (U.S. federal government or U.S. government) is the common government of the United States. The U.S. federal government is composed of three distinct branches, legislative, executive, and judicial. Powers of these three branches are defined and vested by the U.S. Constitution, which has been in continuous effect since May 4, 1789. The powers and duties of these branches are further defined by Acts of Congress, including the creation of executive departments and courts subordinate to the U.S. Supreme Court.
https://en.wikipedia.org/wiki/Federal_government_of_the_United_States